Surgical microscope drape with removable lens assembly

ABSTRACT

The present invention relates to a surgical microscope drape with a removable lens assembly for use with surgical microscopes. The drape assembly comprises an elongated hollow enclosure of sheet-form material having a first end defining an access opening and a second end defining a hole and at least four ocular pockets. The access opening enables the drape assembly to be pulled over the body of a surgical microscope while the four ocular pockets each cover corresponding ocular ports of the microscope. A view portal located on the enclosure at the hole is adapted to be located within a cavity of the objective lens barrel. The portal houses a removable lens assembly that includes a window. Multiple lens assemblies can be packaged together with a microscope drape to form a kit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.10/395,757, filed Mar. 24, 2003 now U.S. Pat. No. 6,902,278 by Andrew J.Bala, which is hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a surgical microscope drape assembly, theassembly providing a removable lens window covering.

BACKGROUND OF THE INVENTION

Microscopes are often used in operating rooms during surgicalprocedures. During many of these procedures, such as spinal and cranialprocedures, the surgeon must manipulate exceptionally small bloodvessels, nerve bundles, muscles, nerves and other tissue. Theseprocedures require viewing the surgical site through a surgicalmicroscope so that the fine details in the surgical site can be clearlyseen by the surgeon. However, during an operation, the area around thesurgical site must remain sterile. A surgical field, as present in atypical hospital's operating room, is an environmentally controlled areawhere the risk of infection from naturally occurring organisms, such asbacteria, is minimized. The environment's sterility is thus controlledby limiting the introduction of infection-causing bacteria and othercontaminants by maintaining strict control over the personnel andequipment present in an operating room.

As it is difficult or impossible to sterilize the surgical microscope,it is common practice to cover the microscope with a sterile drape. Thedrape typically comprises a flexible tube of sheet-form material thatcovers all of the components of the surgical microscope, to include theocular ports of the microscope head and the structure that supports thehead. The drape also typically includes a transparent window therein forattachment to the objective lens of the microscope. The drape istypically manufactured and packaged in a sterile condition so that whenit is unpackaged in the operating room and placed on a microscope, itcreates a sterile field around the microscope and its components.

However, various disadvantages have been realized in trying to adaptsterile drapes to surgical microscopes. One disadvantage arises becausemany hospitals utilize different configurations of microscopes toperform different types of surgical procedures. Microscopes can beconfigured to include a variety of ocular view ports in a variety oflocations, with such configuration depending on the surgical procedureto be performed. The number and location of ocular ports of a givenmicroscope depends on the surgical procedure taking place and the numberof surgeons and or assistants present during the procedure. For example,during cranial operations, surgeons typically stand at the head of thepatient side-by-side of one another, with a lead surgeon standing nextto one or more assisting surgeons. Thus, with the cranial configuration,the microscope may have up to three ocular ports located approximatelyside-by-side of one another on one side of the microscope.

This ocular port configuration changes for spinal operations, wheresurgeons typically stand on opposite sides of a given patient, with alead surgeon and an assisting surgeon standing preferably 180 degreesfrom one another on opposite sides of a patient, and up to two assistingsurgeons standing on either side of the lead surgeon. With the cranialconfiguration, the microscope may thus have up to three ocular portslocated approximately side-by-side of one another on one side of themicroscope and a fourth ocular port located on an opposite side of themicroscope, preferably 180 degrees from the lead surgeon's ocular port.

To effectively cover the microscope, it is usually necessary to form themicroscope drape with one or more ocular pockets to accommodate themicroscope's ocular ports. Prior art drapes have up to three ocularpockets to accommodate the ocular ports of a given microscope. Althoughsuch drapes have proven sufficient for use with microscopes configuredfor cranial operations, with the three ocular pockets accommodating theup to three ocular ports located on one side of a microscope, they proveinsufficient during cranial operations requiring the use of four ocularports. Furthermore, the prior art drapes, having up to three ocularpockets located side-by-side of one another, prove insufficient for useduring cranial procedures utilizing as few as two ocular ports, with thetwo ocular ports used during such procedure being located preferably 180degrees from one another.

For the prior art drapes to accommodate a microscope having two ocularports configured for a cranial operation (i.e. located preferably 180degrees from one another), the ocular pockets of the prior art drape,located side-by-side of one another, must be stretched across the headof the microscope to cover the two opposing ports. Such stretchingusually causes tension at some portions of the drape, especially at thejoint between the main cover portion and the ocular pockets, thuscausing the drape material to deform, rip or rupture. Such a rupturecompromises the sterile field established by the drape, requiring areplacement of the drape itself.

Furthermore, in positioning the prior art drapes on the microscope toaccommodate the opposing ocular ports, a tearing of the drape may occuraround the drape's lens cover, which is typically mounted to theobjective lens barrel of the microscope, again compromising the sterilefield. Although such tearing may be avoided through a rotation of thelens cover about microscope's objective lens barrel, a rotationaladjustment of the lens cover about the barrel may interfere with theoptical quality of the image received through the objective lens anddrape lens cover. Thus there is a need for a microscope drape having aquantity and location of ocular pockets that can readily accommodate thevarious configurations of microscope ocular ports commonly used during avariety of surgical procedures.

Another disadvantage associated with prior art drapes arises where thelens cover of such drapes is mounted to the objective barrel such thatthe lens or window of the cover is located below the lower end of thebarrel itself. Such drape lens covers thus result in an increasedworking distance (depth) of the microscope head during surgicalprocedures. This increased depth of the microscope results in longerworking distances for the surgeon, thus requiring the surgeon to extendhis or her arms during surgical procedures performed while viewing thesurgical site through the microscope. An increased extension of the armsof the surgeon thus results in the surgeon having reduced surgicalcontrol, increased arm and hand fatigue and decreased hand and fingerdexterity.

The location of the drape window below the objective lens barrel alsoresults in the window being located towards the surgical site, thusincreasing the likelihood of the occurrence of view obstructions on thewindow due to blood or tissue particles contacting the window itself.During a given surgical procedure, the microscope head may berepositioned many times in relation to the surgical site. Thus, a windowlocation below the objective lens barrel increases the possibility ofthe surgeon contacting the window with his or her hands, with suchcontact again resulting in viewing obstructions occurring on the window.Thus, there is a need for a microscope drape having a lens cover with awindow location that results in a reduced working distance (depth) ofthe microscope head during surgical procedures and a minimization of theoccurrence of view obstructions on the window, due to blood or tissueparticles contacting the window itself or due to an inadvertent touchingof the window by medical staff.

Undesirable complications may also arise where the placement of thedrape window below the lens barrel interferes with the surgicalprocedure itself. For example, the distal end of a surgeon's hand-heldinstruments may contact or collide with the window during use, thusresulting again in viewing obstructions occurring on the window. Such acollision of the instrument with the window may also interfere with thesurgical procedure itself, thus slowing the procedure or adverselyaffecting the interaction between the instrument and the tissuecontacted thereby within the surgical site. Thus, there is a need for amicroscope drape having a lens cover with a window location that resultsin a reduced working distance (depth) of the microscope head duringsurgical procedures and a minimization of the occurrence surgicalinterference in the form of collisions between the window of the drapeand the hand-held instruments of the surgeon.

In many surgical microscopes, the objective lens transmits light from alight source to the surgical site to illuminate the surgical site, withthe objective lens also transmitting the image of the surgical site tothe optical path of the microscope. Another disadvantage associated withprior art drapes thus arises where the lens cover results in a degradedoptical quality of the viewed image due to a reflection of light fromthe microscope's light source off of the window of the drape lens andtowards the objective lens of the microscope, resulting in glare. In anattempt to remedy this undesirable light reflection and glare, prior artdrapes have utilized convex, concave or otherwise curved lens covers orwindows to direct the light reflection away from the objective lens.

However, such lenses may cause a distortion of the view of the operativefield, resulting in some surgeons discarding the lens or window of thedrape lens cover during a given surgical procedure, thus compromisingthe sterile field around the microscope. With the drape window removed,bacteria or other contaminants present on the objective lens of themicroscope itself may fall into the surgical site, thus increasing alikelihood for the occurrence of infection. A removal of the drapewindow also causes the objective lens of the surgical microscope itselfto become exposed to blood and other fluids so that frequent cleaningmay be required, thus increasing the potential to scratch or damage theobjective lens, an expensive component of the surgical microscope.Finally, a curved drape lens or window results in an undesirablediffraction of a laser beam projected through the lens duringimage-guided surgeries. Thus, there is a need for an objective lenscover that maintains true sterility within the surgical field andminimizes the occurrence of glare, image distortion and laserdiffraction during operative procedures.

Another problem that arises during certain surgical procedures such aspower drilling on bone is that the lens can be obstructed or damaged bysurgical debris. While a window covering the lens protects the expensiveobjective lens of the microscope from physical damage, the opticalproperties of the disposable lens cover itself can be degraded from viewobstructions resulting from blood, bone, or tissue debris. Owing totheir mass produced and disposable nature, lens covers packaged withsurgical drape assemblies often have less than desirable opticalqualities. The additional refraction of light rays caused by adisposable lens cover leads to unacceptable optical aberrations inprecise procedures such as image guide measurements. It would thus bedesirable in these situations for a surgeon to be able to temporarilyremove the lens cover or to replace a defective or dirty lens cover witha clean sterile lens cover.

Accordingly, there remains a need for a true, sterile surgicalmicroscope drape with a removable lens assembly. A removable lensassembly would permit a surgeon to easily replace a lens cover that isdamaged or obstructed with debris with a clean and sterile one. Theremovable lens cover can also be temporarily removed to avoid opticalaberrations in performing delicate surgical tasks. The present inventionsatisfies these needs.

SUMMARY OF THE INVENTION

The present invention generally relates to a drape assembly for use withsurgical microscopes. An exemplary surgical microscope may include atleast first and second ocular ports, an objective lens barrel, and anillumination source (not illustrated) for illuminating the operativefield viewed through the microscope. In one embodiment of the invention,the drape assembly comprises an elongated hollow enclosure of sheet-formmaterial having a first end defining an access opening and a second enddefining a hole and at least 4 ocular pockets. In the preferredembodiment of the invention, the sheet-form material is a transparent,flexible material made of polyethylene, polypropylene, or some othersimilar polymer or copolymer film of a predetermined thickness.

The access opening of the enclosure allows access to the interior of theenclosure to enable the drape assembly to be pulled over the body of asurgical microscope. The access opening is thus pulled over and past thehead of the microscope to a location on the microscope away from thehead and operative field. The at least four ocular pockets defined inthe second end of the enclosure each cover a corresponding ocular portof the microscope when the drape assembly is pulled over the microscopeas described above. The at least four ocular pockets enable the drapeassembly to be used on a variety of microscope heads having a variety ofocular ports placed in a variety of locations, with the number andlocation of ocular ports of a given microscope depending on the surgicalprocedure taking place and the number of surgeons and or assistantspresent during the procedure.

A view portal is preferably located at the hole on the enclosureproximal to the second end. The view portal includes a cylindricalframe, defining a central axis, and an outer surface engageable with aninner peripheral wall of the objective lens barrel for mounting theframe on the barrel. The cylindrical frame includes a window attached toa window support located at a first end of the frame, with the windowsupport adapted to be located within a cavity of the objective lensbarrel when the outer surface of the cylindrical frame engages the innerperipheral wall. A flange, located proximal to a second end of thecylindrical frame and extending outwardly from the frame's outersurface, is adapted for attachment to the sheet-form material of thedrape assembly about the hole the enclosure to form a hermeticallysealed connection between the two.

The window, located on the window support, is thus located within thecavity of the objective lens barrel when the outer surface of the frameengages the inner peripheral wall of barrel. The location of the windowwithin the cavity is advantageous because it results in a reducedworking distance (depth) of the microscope head during surgicalprocedures and a minimization of surgical interference and of viewingobstructions from occurring on the window itself. The window of the viewportal intersects a pair of viewing axes defined by the ocular ports ofthe microscope and an illumination axis defined by an illuminationsource within the microscope when the frame is mounted on the barrel.

The window of the view portal is flat and acutely inclined to minimizeglare from the illumination source, with the window defining a planeacutely inclined in relation to the central axis of the frame or inrelation to the illumination axis of the microscope and the uppersurface of the window receiving the illumination axis from theillumination source. In another embodiment of the invention, theanti-glare properties of the inclined window are enhanced through theaddition of at least one layer of anti-reflective coating to at leastthe upper surface of the window receiving the illumination axis from theillumination source.

Optimal viewability through the window occurs when the view axes fall ona common elevation of the inclined window, with the view portal mountedon the objective lens barrel to have a rotational orientation of thewindow inclination preferably towards the first ocular port or secondocular port of the microscope to ensure such optimal viewability. Alocator is preferably located on the cylindrical frame to rotationallyorient the view portal of the drape assembly in relation to theobjective lens barrel of the microscope when mounted thereon.

A particularly preferred aspect of the present invention provides a lensassembly that is removable mountable within the cylindrical frame of theview portal. The lens assembly includes a window secured to a windowsupport that can be easily removed from the view portal and replacedwith a new window support and window. Multiple lens assemblies can bepackaged together with a microscope drape to form a kit.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of an exemplary surgical microscope;

FIG. 2 is a plan view of the drape assembly;

FIG. 3 is a partial sectional elevational view of the objective lensbarrel of the microscope and the view portal of the drape assembly;

FIG. 4 is a plan view of the view portal of the drape assembly showingan upper surface of the window;

FIG. 5 is a partial sectional elevational view of the objective lensbarrel of the microscope, the view portal of the drape assembly, and aremovable lens assembly;

FIG. 6 is a perspective view of the removable lens assembly with apartial sectional view of a window; and

FIG. 7 is view of a box kit including a microscope drape assembly andseveral removable lens assemblies.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally relates to a drape assembly for use withsurgical microscopes. FIG. 1 is a perspective view illustrating thebasic components of an exemplary surgical microscope 10 to be covered byone embodiment of the drape assembly of FIG. 2. The microscope 10 isadjustably mounted relative to a floor, wall or ceiling mountedstructure (not shown) with an articulated support arm 20 supporting amicroscope head 30. The microscope head 30, mounted to the free end ofthe support arm 20, includes at least first and second ocular ports 40and 50, an objective lens barrel 60, and an illumination source (notillustrated) for illuminating the operative field viewed through themicroscope.

FIG. 2 illustrates one embodiment of the microscope drape assembly 70that covers the surgical microscope 10 of FIG. 1 while FIGS. 3 and 4illustrate more detailed views of the view portal of the assembly. Inthe embodiment shown in FIG. 2, the drape assembly 70 comprises anelongated hollow enclosure 80 of sheet-form material having a first end90 defining an access opening 100 and a second end 110 defining a hole120 and at least 4 ocular pockets 130, 140, 150 and 160. A view portal170 is preferably located at the hole 120 on the enclosure proximal tothe second end 110. Referring to FIGS. 3 and 4, the view portal 170includes a cylindrical frame 180, defining a central axis 190, and anouter surface 200 engageable with an inner peripheral wall 62 of theobjective lens barrel 60, for mounting the frame on the barrel.

The cylindrical frame 180 includes a flat window 210 attached to awindow support 220 located at a first end 182 of the frame, with thewindow support adapted to be located within a cavity 64, defined by theinner peripheral wall 62 of the objective lens barrel, when the outersurface 200 of the cylindrical frame 180 engages the inner peripheralwall. The window 210 of the view portal 170 intersects a pair of viewingaxes 260 and 270 defined by the ocular ports of the microscope 10 and anillumination axis 280 defined by an illumination source (not shown)within the microscope 10 when the frame 180 is mounted on the barrel 60.The window of the view portal 170 is acutely inclined to minimize glarefrom the illumination source, with the view portal having a rotationalorientation with the lens barrel to enable an optimum viewabilitythrough the portal. A locator 250 is preferably located on thecylindrical frame 180 to rotationally orient the view portal 170 of thedrape assembly 70 in relation to the objective lens barrel 60 of themicroscope 10 when mounted thereon.

Referring again to FIG. 2, the drape assembly 70 has a body thatcomprises a substantially tubular, elongated hollow enclosure 80 made ofa sheet-form material. In the preferred embodiment of the invention, thesheet-form material is a transparent, flexible material made ofpolyethylene, polypropylene, or some other similar polymer or copolymerfilm of a predetermined thickness. A first end 90 of the enclosure 80defines an access opening 100 while a second or opposite end 110 definesat least four ocular pockets 130, 140, 150, 160 and a hole 120.

The access opening 100 of the enclosure 80, defined by the periphery ofthe tubular enclosure 80 at the first end 90, allows access to theinterior of the enclosure 80 to enable the drape assembly 70 to bepulled over the body of a surgical microscope 10. The access opening 100is thus pulled over and past the head 30 of the microscope (FIG. 1) to alocation on the microscope away from the head and operative field (i.e.where the support arm meets the floor, wall or ceiling of the operatingroom). The at least four ocular pockets 130, 140, 150 and 160, definedin the second end 110 of the enclosure 80, each cover a correspondingocular port (if present for each pocket) of the microscope 10 when thedrape assembly 70 is pulled over the microscope as described above.

The at least four ocular pockets 130, 140, 150 and 160 enable the drapeassembly 70 to be used on a variety of microscope heads having a varietyof ocular ports placed in a variety of locations. The number andlocation of ocular ports of a given microscope depends on the surgicalprocedure taking place and the number of surgeons and or assistantspresent during the procedure. For example, during cranial operations,surgeons typically stand at the head of the patient side-by-side of oneanother, with a lead surgeon standing next to an assisting surgeon. Withthis configuration, the microscope head 30 typically has a first ocularport 40, used by the lead surgeon and centrally located on themicroscope head 30 as illustrated in FIG. 1, and a second ocular port(not shown), used by the assisting surgeon and located to the right orleft of the first ocular port 40. It is noted that a third ocular port(not shown) may also be utilized during a given cranial procedure, withthe third ocular port being located next to the first ocular port 40 ona side opposite the second ocular port. Thus, during cranial operations,up to three ocular ports may be used during a given procedure, with thethree ports being located approximately side-by-side of one another onone side of the microscope's head 30.

During spinal operations, however, surgeons typically stand on oppositesides of a given patient, with a lead surgeon standing on one side ofthe patient and an assisting surgeon standing on the opposite side ofthe patient, preferably 180 degrees from or facing the lead surgeon.With this configuration, as illustrated in the microscope of FIG. 1, themicroscope head 30 typically has a centrally located first ocular port40 used by the lead surgeon, with a second ocular port 50 used by theassisting surgeon centrally located preferably 180 degrees from thefirst ocular port. Although the ocular ports of the lead and assistantsurgeon are located 180 degrees from one another in the preferredembodiment of the microscope, the location of the ocular ports from oneanother may be of any angle that enables the surgeons to stand onopposite sides of the patient.

Although not illustrated, an additional assistant or observer may standon each side of the lead surgeon or assisting surgeon, thusnecessitating the use of one or more additional ocular ports, with theone or more additional ocular ports being respectively located on eachside of the lead or assistant surgeon's respective first or secondocular port 40 or 50. With this configuration, three ocular ports canthus be located on one side of the microscope head 30 (one on each sideof the centrally located first or second ocular ports 40 or 50), withthe first and second ocular ports 40 and 50 being located preferably 180degrees from one another. Thus, during spinal operations, up to fourocular ports may be used during a given procedure, with three ocularports being located on one side of the microscope head 30 and patient.

The drape assembly of FIG. 2 thus includes at least 4 ocular pockets130, 140, 150 and 160 to accommodate the microscope configurationsrequisite of both cranial and spinal operations. For spinal operationsutilizing a lead and assisting surgeon and two assistants or observers(three side-by-side ocular ports and one ocular port located preferably180 degrees of a first port), the drape assembly includes a firstcentrally located ocular pocket 130 with a second centrally locatedocular pocket 140 located preferably 180 degrees from the first pocket.In the embodiment of the invention illustrated in FIG. 2, third andfourth ocular pockets 150 and 160 are located on opposite sides of thefirst pocket 130. This configuration of ocular pockets thus enables thedrape assembly to accommodate a surgical microscope having 4 ocularports, as described above, with three of the four ocular ports beinglocated on one side of the microscope's head. For cranial operations,however, the first, third and fourth ocular pockets 130, 150 and 160 canaccommodate the three ocular view ports located on one side of themicroscope head 30. The second ocular pocket 140, located preferably 180degrees from the first pocket 130, would go un-used during thisprocedure.

The use of 4 ocular pockets 130, 140, 150 and 160 with the microscopedrape assembly thus have the advantage of allowing a single drapeassembly to accommodate various surgical procedures, with each procedurehaving a different ocular port configuration. The use of 4 ocularpockets also has the advantage during spinal procedures of not requiringthat the drape assembly enclosure 80 (i.e. an assembly having less thanfour ocular pockets) be stretched or the view portal 170 be rotatedabout the objective lens barrel 60 to accommodate the ocular portlocated 180 degrees from the first port. Such a stretching of theenclosure 80 can compromise the sterile field established by the drapeassembly around the microscope, while the rotation of the view portal170 can compromise the quality of the image received by the objectivelens of the microscope.

Located on the enclosure 80 proximal to the ocular ports at theenclosure's second end 110 is hole 120. The hole, having a diameter ofpredetermined dimension to accommodate the view portal 170 therein, islocated preferably on a lower surface 82 of the enclosure 80 to allowthe view portal to be mounted on the objective lens barrel 60, locatedon the lower surface of the microscope head 30. The view portal 170,adapted to be mounted on the objective lens barrel 60 of the microscope,is attached to the sheet-form material of the enclosure 80 about thehole 120 such that the drape assembly 70 is sealed around the viewportal 170.

FIGS. 3 and 4 respectively show a side sectional view and plan view ofthe preferred embodiments of the view portal 170. View portal 170comprises a cylindrical frame 180 defining first and second ends 182 and184 and a central axis 190. The cylindrical frame 180 has an outersurface 200 engageable with the inner peripheral wall 62 of theobjective lens barrel 60 for mounting the frame on the barrel. In oneembodiment of the invention, the outer surface 200 of the frame 180 caninclude at least one raised resilient surface 202 engageable with theinner peripheral wall 62 of the objective lens barrel 60. In theembodiment shown in FIGS. 3 and 4, at least one raised resilient surfaceis comprised of at least one bump or nodule located on the outer surface200 of the frame 180.

In another embodiment of the invention, the outer surface 200 of theframe 180 can include at least one tab 204 engageable with at least onerecess 66 located within the inner peripheral wall 62 of the objectivelens barrel 60. With such an arrangement, the at least one tab 204 ofthe frame 180 is aligned with an at least one recess opening 69, locatedat the bottom of the inner peripheral wall 62 of the barrel, and the atleast one tab is inserted into the opening and the frame 180 raised androtated until the at least one tab is seated in the at least one recess66. It is noted that the at least one raised resilient surface 202 andthe at least one tab 204 are illustrated in FIGS. 3 and 4 in combinationwith one another to engage the frame 180 to the inner peripheral wall.However, it is understood that the two can be used in the alternative aswell to engage the frame 180 to the inner peripheral wall of themicroscope's objective lens barrel 60.

A window support 220 is located proximal to the first end 182 of thecylindrical frame 180 and is adapted to be located within the cavity 64of the objective lens barrel 60 when the outer surface 200 of the frameengages the inner peripheral wall 62 of the barrel. The window support220 is preferably a shelf upon which an outer periphery of the window210 rests when located within the frame 180. The window 210, located onthe window support 220, is thus located within the cavity 64 of theobjective lens barrel 60 when the outer surface 200 of the frame 180engages the inner peripheral wall 62 of barrel 60.

The location of the window 210 within the cavity 64 is advantageousbecause it results in a reduced working distance (depth) of themicroscope head during surgical procedures. The reduced depth of themicroscope allows for shorter working distances for the surgeon, thusnot requiring the surgeon to extend his or her arms during surgicalprocedures performed while viewing the surgical field through themicroscope. A reduced extension of the arms of the surgeon thus enablesthe surgeon to have better surgical control, less arm and hand fatigue,and improved hand and finger dexterity. The location of the window 210within the cavity 64 is also advantageous because the window is moved upand away from the surgical field, thus minimizing surgical interferenceand view obstructions from occurring on the window due to blood ortissue particles contacting the window itself. The location of thewindow 210 within the cavity 64 also minimizes the possibility of thesurgeon contacting the window with his or her hands, with such contactagain resulting in viewing obstructions occurring on the window.

Turning again to FIGS. 3 and 4, the window 210 is located on the windowsupport 220 such that the window intersects a pair of viewing axes 260and 270 and an illumination axis 280 of the microscope, if anillumination source is utilized therein. The pair of viewing axes 260and 270 are defined by the spaced oculars of each ocular port, thusenabling stereoscopic viewing of the field of operation through eachport of the surgical field via the path of the viewing axes through themicroscope's objective lens barrel 60 and view portal window 210. Theillumination axis 280, if present, is defined by an illumination source(i.e. a xenon light source, not shown), preferably located within themicroscope's head 30, that transmits the illumination axis through themicroscope's objective lens barrel 60 and through the window 210 of viewportal 170, the window having an upper surface 212 receiving theillumination axis from the illumination source to illuminate the fieldof operation.

Referring to FIG. 3, to minimize any glare that may occur on theobjective lens in the viewing axes 260 and 270 due to the reflection ofthe illumination axis 280 from the window 210 of the view portal 170, inone embodiment of the invention, the window 210 defines a plane acutelyinclined in relation to the central axis 190 of the frame 180, with thewindow defining the plane having an upper surface 212 receiving theillumination axis from the illumination source. In the preferredembodiment of the invention utilizing a window 210 inclination inrelation to the frame central axis 190, the angle α of the acuteinclination of the window in relation to the frame central axis is fromabout 81 degrees to about 85 degrees, preferably from about 81 degreesto about 83 degrees, and optimally about 82 degrees.

Alternatively, the window 210 defines a plane acutely inclined inrelation to the illumination axis 280 of the microscope, with the uppersurface 212 of the window 210 defining the plane receiving theillumination axis from the illumination source. In the preferredembodiment of the invention utilizing a window 210 inclination inrelation to the illumination axis 280, the angle β of inclination of thewindow in relation to the illumination axis is from about 77 degrees toabout 83 degrees, preferably from about 77 degrees to about 81 degrees,and optimally about 79 degrees. The angle of the window 270 in relationto the illumination axis 280 takes into account that the illuminationaxis 280 of the type of microscope shown can have an angle of from about2 degrees to about 4 degrees in relation to the central axis 190 of theframe 180. The inclination of the window 210, whether in relation to thecentral axis 190 of the frame 180 or in relation to the illuminationaxis 280 of the microscope, minimizes any glare or reflection from theillumination axis because any reflection of the illumination axis fromthe window is deflected away from the viewing axes 260 and 270.

In yet another embodiment of the invention, the anti-glare properties ofthe inclined window 210 are enhanced through the addition of at leastone layer of anti-reflective coating 214 to at least the upper surface212 of the window receiving the illumination axis 280 from theillumination source. The coating 214 can also be applied to at least thelower surface of the window as well. In the preferred embodiment of theinvention utilizing an anti-reflective coating, a coating comprised ofabout 40% zirconia (ZrO2) and about 60% fluoride (MgF2) is applied by amachine (i.e. Optorum Model No. OTFC-1100DB) to the inclined window inabout 3 layers to form a coating thickness of about 0.0045 mm.

The zirconia-fluoride coating, having an affinity to absorb redwavelengths of from about 480 nm to about 550 nm, has an index ofrefraction of about 2.1 on a window having an index of refraction ofabout 1.6. The coating also has an angle of incidence of from about 0 toabout 15, with a reflectance of less than about 2% to yield stray lightof less than about 0.8%. When the zirconia-fluoride coating is appliedto the upper surface 212 of the window 210 receiving the illuminationaxis 280 from the illumination source, the inclined window, having anindex of refraction of about 1.6, and the zirconia-fluoride coating,having an index of refraction of about 2.1, will have an enhancedminimization of the occurrence of glare.

Because the ocular ports define a pair of illumination axes 260 and 270to enable a stereoscopic view of the operative field, optimalviewability through the window 210 occurs when each axis of the pairfalls on a common elevation of the inclined window. Referring now toFIG. 4, to enable the viewing axes 260 and 270 to fall on a commonelevation of the inclined window 210, the view portal 170 is mounted onthe objective lens barrel 60 to have a rotational orientation to thelens barrel which ensures that the viewing axes intersect a planedefined by the inclined window 210 to establish an intersection axis 300substantially normal to an imaginary line intersecting the frame centralaxis 190 and perpendicular to the central axis 190 itself. Thus, optimumviewability through the window 210 of the view portal 170 is ensured ifthe acute inclination of the window defined by the intersection axis 300is directed towards the first ocular port 40 of the microscope of FIG.1, or away from the first ocular port and towards the second ocular port50, which is preferably located 180 degrees from the first ocular port.Such a rotational orientation also has the advantage of providing aconstant laser divergence that can be programmed into the computerduring image guided procedures.

For a view portal 170 utilizing at least one tab 204 on its frame outersurface 200 for engagement with the recess 66 of the objective lensbarrel inner peripheral wall 62, the direction of acute inclination ofthe window 210 can be rotationally oriented with the at least one tab,and the recess similarly rotationally oriented within the lens barrel,to ensure that the direction of inclination is towards either the firstor second ocular ports 40 or 40 when the tab of the frame engages therecess of the barrel. For a view portal 170 utilizing at least oneraised resilient surface 202 on its frame outer surface 200 forengagement with the objective lens barrel inner peripheral wall 62, thedirection of acute inclination of the window 210 can be indicated by alocator 250 rotationally oriented with and attached to the cylindricalframe 180 of the view portal 170. In the embodiment of the inventionillustrated in FIG. 3, the locator is preferably comprised of a button252 located on a first of two grips 254 and 256 extending downwardlyfrom the second end 184 of the frame 180. The two grips 254 and 256provide a gripping surface of the view portal 170 for the surgeon tohold when mounting the portal on the objective lens barrel. The button252 indicates to the surgeon that the view portal 170 should be mountedon the lens barrel 60 with the button 252 facing preferably either thefirst or second ocular port 40 or 50 of the microscope 10, depending onthe type of operation performed. Although button 252 is used as thelocator 250 in the preferred embodiment of the drape assembly 70, it isunderstood that other visual or tactile indications (i.e. a line) may beutilized to indicate the preferred rotational orientation as well.

It is noted that the addition of a fourth ocular pocket to the drapeassembly 70 (i.e. the addition of ocular pocket 140) is beneficial tothe rotational orientation of the view portal 170 to the objective lensbarrel 60. After mounting the view portal 170 on the objective lensbarrel 60 with a rotational orientation to establish optimum viewabilitythrough the portal, the fourth ocular pocket 140 of the drape isavailable for placement over second ocular port 50, located preferablyopposite from the first ocular port 40 during spinal operations, withoutrequiring the view portal to be removed from the barrel to allow arotation of the hollow enclosure 80 to accommodate the second ocularport. Such a procedure is routinely required with prior art drapeshaving less than 4 ocular pockets, with the disconnection of the viewportal 170 from the objective lens barrel 60 having the undesirable sideeffect of compromising the optimal viewability of the view received bythe objective lens.

Returning to a discussion of the components of the view portal 170, aflange 310 is located proximal to the second end 184 of the cylindricalframe 180, extending outwardly from the frame's outer surface 200. Asshown in FIGS. 3 and 4, the flange 310 is adapted for attachment to thesheet-form material of the drape assembly 70 about the hole 120 of theenclosure 80 to form a hermetically sealed connection between the two.The sheet-form material may be attached to the flange via adhesives,heat bonding, or other similar methods understood in the art. While thesheet-form material is shown in FIGS. 3 and 4 as being attached to asurface of the flange 310 facing the window 210, it is understood thatthe material can be attached to the opposite surface of the flange, aswell as the outer peripheral surface thereof. Thus, with the sheet formmaterial attached to the flange 310 of the cylindrical frame 180, theframe and window of the view portal 170 seals the hole 120 in theenclosure 80.

In use, the access opening of the first end of the hollow enclosure ofthe drape assembly is pulled over a given surgical microscope so thatthe access opening is located away from the microscope's head. Thesecond end of the hollow enclosure of the drape assembly is pulled overthe head of the microscope, with the view portal of the drape assemblylocated on a lower surface of the enclosure proximal to the microscope'sobjective lens barrel. The grips of the view portal are held as thefirst end of the cylindrical frame and window of the portal is insertedinside the cavity of the lens barrel. If the view portal includes atleast one tab on the outer surface of the frame, the at least one tab isinserted into an at least one recess opening located at the bottom ofthe inner peripheral wall of the lens barrel and the frame and the frameis raised and rotated until the at least one tab is seated in the leastone recess of the lens barrel inner peripheral wall.

The engagement of the tab and recess ensures that the view portal isproperly rotationally oriented to the lens barrel with the acuteinclination of the window facing either the first or second view portsof the microscope. If the view portal utilizes a raised resilientsurface on the frame outer surface to engage the inner peripheral wallof the barrel, the view portal is rotated on the barrel to ensure thatthe button locator of the first grip is directed towards the first orsecond view ports. After the view portal is mounted on the barrel andthe rotational orientation between the two is established, the hollowenclosure is positioned about the microscope so that the ocular pocketsof the enclosure cover the corresponding ocular ports of the microscope.When the surgical procedure has concluded, the view portal is removedfrom the objective lens barrel and the enclosure and ocular pockets arepulled from the head of the microscope until the passageway located atthe first end of enclosure is pulled over the microscope's head, thusremoving the drape assembly from the microscope.

FIGS. 5 and 6 show another preferred embodiment of the invention whereinthe window support is removable from the cylindrical frame. Windowsupport 420 can take the form of a resilient circumferential band thatis removable from the cylindrical frame 180. The window support 420 hasthe same angle of inclination as that of the cylindrical frame 180. Thewindow support 420 has an outer diameter X that is substantially thesame as the inner diameter Y of the cylindrical frame 180 so that thecylindrical frame 180 snugly engages the window support 420 within theframe 180. The window support 420 and the frame 180 is held togetherthrough an insert tab 440 on the window support 420 that fits intorecess 450 on the cylindrical frame 180. The window support 420 and theframe 180 can also be held together through means such as contactfriction, a raised resilient surface or other means.

Window support 420 fixedly supports a window 415 that serves as aprotective lens cover for the objective lens of the microscope. Thewindow 415 is secured between a ledge 423 and ridges 424 on the insidesurface of window support 420. Alternatively, window 415 can be securedto the window support 420 through friction, adhesive, welding, tab andrecess or other securing means. Together, the window support 420 and thewindow 415 form a lens assembly 410 that can be removably mounted withthe cylindrical frame. When so mounted, the window 420 and windowsupport 415 of the lens assembly 410 and the cylindrical frame 180 sealsthe hole in the enclosure.

The window support 420, preferably formed of a resilient material suchas plastic, preferably also includes at least two tabs 430 that areintegrally formed with the band. The tabs 430 preferably have aplurality of ridges to facilitate tactile grip by the surgeon. Inoperation, the lens assembly 410 can be removed from the cylindricalframe 180 and view portal 170 by squeezing the two tabs 430. This causesthe resilient band of the window support 420 to bend and disengage fromthe cylindrical frame 180. The same lens assembly 410 can also belikewise reinserted into the cylindrical frame 180. Alternatively, adifferent lens assembly 410 containing a different window support 420and a different window 415 exchanged for the removed lens assembly 410.

The lens assemblies 410 of the present invention use an interchangeablewindow support and vary by the type of window that is fixedly secured tothe window support. The window supports of the different lens assembliescan be color coded for visual reference to facilitate the rapididentification of one type of lens assembly mounted with a particulartype of window or filter from another. As shown in FIG. 7, a microscopedrape assembly 460 can be packaged together along with multiple lensassemblies 410 as a kit in a box, bag, or other packaging. Sterilizedreplacement lens assemblies containing different types of windows canalso be marketed and packaged separately from the microscope drapeassembly.

Interchangeable lens assemblies permit a surgeon to exchange a lenscover window that is optically defective or has been soiled with blood,bone fragments or other surgical debris with a clean and sterilereplacement. A surgeon can also temporarily remove the lens assembly andwindow during image guided procedures to avoid having the throughmicroscope measurements be altered by refraction through the lensassembly window.

The removability and interchangeabilty of the lens assemblies permit thesurgical microscope to be used for a number of special applications byusing different windows. For example, a particular lens assemblycomprises a window support fixedly supporting a colored filter as awindow. Such a filter is sometimes desirable to enhance the contrast ofcertain features of the optical image through the microscope. Under thepresent invention, a surgeon can easily exchange the lens assemblycontaining a clear window for one with a lens assembly with a coloredfilter.

Still yet another lens assembly comprises a window support fixedlysupporting a fluorescence filter. Patients can be given certain drugsprior to surgery that cause targeted biological structures to fluoresceunder certain conditions. A surgeon can then easily identify thefluorescing tissues of interest through the microscope with a lensassembly mounted with a fluorescence filter. Under the presentinvention, a surgeon can easily change sterilized lens assembliesmounted with different types of filters while protecting the sterilityof the surgical microscope. One of ordinary skill in the art wouldappreciate that the removable lens system of the present invention canbe similarly adapted for any number of special lighting and filteringapplications.

1. A drape assembly for maintaining a sterile field around a surgicalmicroscope having at least one ocular port and an objective lens barrelhaving an inner peripheral wall defining a cavity, the assemblycomprising: an elongated hollow enclosure of sheet-form material havinga first end defining an access opening and a second end defining a hole;a cylindrical frame located on the enclosure second end, the cylindricalframe having an inner surface and an outer surface, the outer surface ofthe frame being engageable with the inner peripheral wall of theobjective lens barrel for mounting the frame on the barrel within thecavity; a window support removably mountable within the cylindricalframe, the window support comprising a resilient circumferential bandand a plurality of spaced integral tabs, the window support furtherhaving an outer diameter substantially the same as the inner diameter ofthe cylindrical frame and an outer surface removably engageable with theinner surface of the cylindrical frame; and a window matingly engagedwith the window support, the frame, window support and window sealingthe hole in the enclosure when the window support is removably mountedwithin the cylindrical frame.
 2. The drape assembly of claim 1 whereinthe engageable outer surface of the cylindrical frame includes at leastone raised resilient surface engageable with the inner peripheral wallof the objective lens barrel.
 3. The drape assembly of claim 1 whereinthe engageable outer surface of the cylindrical frame includes at leastone tab engageable with at least one recess located within the innerperipheral wall of the objective lens barrel.
 4. The drape assembly ofclaim 1 wherein the engageable outer surface of the window supportincludes at least one raised resilient surface engageable with the innersurface of the cylindrical frame.
 5. The drape assembly of claim 1wherein the engageable outer surface of the window support includes atleast one tab engageable with at least one recess located within theinner surface of the cylindrical frame.
 6. A view portal for a surgicalmicroscope drape for maintaining a sterile field around a surgicalmicroscope, the drape defining an elongated hollow enclosure ofsheet-form material having an access opening located at one end and ahole located proximal to an opposite end, the microscope having at leastone ocular port and an objective lens barrel having an inner peripheralwall defining a cavity, the portal comprising: a cylindrical framedefining first and second ends, having an outer surface releasablyengageable with the inner peripheral wall of the objective lens barrelfor mounting the frame within the cavity of the objective lens barrel; aflange located proximal to the second end of the cylindrical frame andextending outwardly of the frame's outer surface, the flange adapted forattachment to the sheet-form material of the drape about the hole; awindow support removably mountable within the cylindrical frame, thewindow support having an outer surface removably engageable with theinner surface of the cylindrical frame, the window support furtherhaving an outer diameter substantially the same as the inner diameter ofthe cylindrical frame; and a window matingly engaged with the windowsupport adapted to be located within the cavity of the objective lensbarrel when the window support is removably mounted within thecylindrical frame.
 7. The view portal of claim 6 wherein the engageableouter surface of the cylindrical frame includes at least one raisedresilient surface engageable with the inner peripheral wall of theobjective lens barrel.
 8. The view portal of claim 6 wherein theengageable outer surface of the cylindrical frame includes at least onetab engageable with at least one recess located within the innerperipheral wall of the objective lens barrel.
 9. The view portal ofclaim 6 wherein the engageable outer surface of the window supportincludes at least one raised resilient surface engageable with the innersurface of the cylindrical frame.
 10. The view portal of claim 6 whereinthe engageable outer surface of the window support includes at least onetab engageable with at least one recess located within the inner surfaceof the cylindrical frame.
 11. A kit for a drape assembly for maintaininga sterile field around a surgical microscope having at least one ocularport and an objective lens barrel having an inner peripheral walldefining a cavity, the kit comprising: an elongated hollow enclosure ofsheet-form material having a first end defining an access opening and asecond end defining a hole; a cylindrical frame located on the enclosuresecond end, the cylindrical frame having an outer surface engageablewith the inner peripheral wall of the objective lens barrel for mountingthe frame on the barrel; and at least two lens assemblies each adaptedto be removably mountable to the cylindrical frame, each lens assemblycomprising a window support and a window matingly secured to the windowsupport, having an outer surface adapted to be removably engageable withthe inner surface of the cylindrical frame.
 12. The kit in claim 11wherein the window in at least one lens assembly is a fluorescencefilter.
 13. The kit in claim 11 wherein the window in at least one lensassembly is a colored filter.
 14. The kit in claim 12 wherein lensassembly comprising the fluorescence filter is of a different color thanother lens assemblies.
 15. The kit in claim 13 wherein the lens assemblycomprising the colored filter is of a different color than other lensassemblies.
 16. The kit in claim 11 wherein the engageable outer surfaceof the cylindrical frame in at least one lens assembly includes at leastone raised resilient surface engageable with the inner peripheral wallof the objective lens barrel.
 17. The kit in claim 11 wherein theengageable outer surface of the cylindrical frame in at least one lensassembly includes at least one tab engageable with one recess locatedwithin the inner peripheral wall of the objective lens barrel.
 18. Thekit in claim 11 wherein the engageable outer surface of the windowsupport in at least one lens assembly includes at least one raisedresilient surface engageable with the inner surface of the cylindricalframe.
 19. The kit in claim 11 wherein the engageable outer surface ofthe window support in at least one lens assembly includes at least onetab engageable with at least one recess located within the inner surfaceof the cylindrical frame.